Question

Which one of the following is a matching pair?

• A. Lubb - sharp closure of AV valves at the beginning of ventricular systole
• B. Dup - sudden opening of semilunar valves at the beginning of ventricular diastole
• C. Pulsation of the radial artery - valves in the blood vessels
• D. Initiation of the heart beat - Purkinje fibres

Answer 1

Answer: (A)

Lubb - sharp closure of AV valves at the beginning of ventricular systole

Answer 2

The gradually increasing contraction of ventricular muscles during systole first causes the closure of bicuspid and tricuspid valves (AV valves), producing a lowpitched "lubb" sound. Later, it causes the opening of the semilunar valves of systemic and pulmonary aorta. At the end of ventricular systole, semilunar valves shut, producing the second, louder heart sound, the "dup". Thus each heart beat is accompanied by a "lubb-dup" sound.